CN112282705A - Evaluation device and experimental method for phase stability of drilling fluid additive to natural gas hydrate - Google Patents
Evaluation device and experimental method for phase stability of drilling fluid additive to natural gas hydrate Download PDFInfo
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- NMJORVOYSJLJGU-UHFFFAOYSA-N methane clathrate Chemical compound C.C.C.C.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O.O NMJORVOYSJLJGU-UHFFFAOYSA-N 0.000 title claims abstract description 281
- 239000012530 fluid Substances 0.000 title claims abstract description 163
- 238000005553 drilling Methods 0.000 title claims abstract description 162
- 239000000654 additive Substances 0.000 title claims abstract description 64
- 230000000996 additive effect Effects 0.000 title claims abstract description 56
- 238000002474 experimental method Methods 0.000 title claims abstract description 36
- 238000011156 evaluation Methods 0.000 title claims abstract description 16
- 239000007789 gas Substances 0.000 claims abstract description 131
- 238000006243 chemical reaction Methods 0.000 claims abstract description 87
- 239000007788 liquid Substances 0.000 claims abstract description 86
- 238000002347 injection Methods 0.000 claims abstract description 57
- 239000007924 injection Substances 0.000 claims abstract description 57
- 230000035699 permeability Effects 0.000 claims abstract description 27
- 238000000354 decomposition reaction Methods 0.000 claims abstract description 26
- 238000005259 measurement Methods 0.000 claims abstract description 24
- 238000000034 method Methods 0.000 claims abstract description 16
- 238000012544 monitoring process Methods 0.000 claims abstract description 16
- 238000009826 distribution Methods 0.000 claims abstract description 12
- 238000003860 storage Methods 0.000 claims description 68
- 238000004088 simulation Methods 0.000 claims description 63
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 60
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 44
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 34
- 239000003345 natural gas Substances 0.000 claims description 31
- 229910001873 dinitrogen Inorganic materials 0.000 claims description 22
- 239000013043 chemical agent Substances 0.000 claims description 16
- 238000011068 loading method Methods 0.000 claims description 15
- 239000007787 solid Substances 0.000 claims description 12
- 238000012545 processing Methods 0.000 claims description 11
- 239000004576 sand Substances 0.000 claims description 10
- 239000013078 crystal Substances 0.000 claims description 9
- 230000008859 change Effects 0.000 claims description 8
- 239000000126 substance Substances 0.000 claims description 8
- 238000011049 filling Methods 0.000 claims description 7
- 238000005086 pumping Methods 0.000 claims description 7
- 230000008054 signal transmission Effects 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- 238000002360 preparation method Methods 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 5
- 230000009471 action Effects 0.000 claims description 4
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 238000013401 experimental design Methods 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 238000007789 sealing Methods 0.000 claims description 3
- 238000003786 synthesis reaction Methods 0.000 claims description 3
- 230000005540 biological transmission Effects 0.000 claims description 2
- 238000007599 discharging Methods 0.000 claims description 2
- 238000011161 development Methods 0.000 abstract description 2
- 230000007246 mechanism Effects 0.000 description 4
- 238000005065 mining Methods 0.000 description 4
- 238000011160 research Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- -1 natural gas hydrates Chemical class 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 230000006641 stabilisation Effects 0.000 description 2
- 238000011105 stabilization Methods 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009795 derivation Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000000706 filtrate Substances 0.000 description 1
- 230000010534 mechanism of action Effects 0.000 description 1
- 239000008239 natural water Substances 0.000 description 1
- 230000009897 systematic effect Effects 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
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- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B49/00—Testing the nature of borehole walls; Formation testing; Methods or apparatus for obtaining samples of soil or well fluids, specially adapted to earth drilling or wells
-
- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09B—EDUCATIONAL OR DEMONSTRATION APPLIANCES; APPLIANCES FOR TEACHING, OR COMMUNICATING WITH, THE BLIND, DEAF OR MUTE; MODELS; PLANETARIA; GLOBES; MAPS; DIAGRAMS
- G09B25/00—Models for purposes not provided for in G09B23/00, e.g. full-sized devices for demonstration purposes
- G09B25/02—Models for purposes not provided for in G09B23/00, e.g. full-sized devices for demonstration purposes of industrial processes; of machinery
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- Engineering & Computer Science (AREA)
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- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
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Abstract
The invention relates to an evaluation device and an experimental method of a drilling fluid additive for natural gas hydrate phase stability, belonging to the technical field of natural gas hydrate development and comprising a gas injection system, a liquid injection system, a vacuumizing system, a natural gas hydrate simulated reservoir system, a reservoir permeability measurement system, a drilling fluid circulating system, a natural gas hydrate simulated reservoir temperature and pressure monitoring system and a reaction kettle temperature control system; the method can simulate the drilling condition of a real horizontal well, realize the real-time measurement of the influence range of the drilling fluid additive in the natural gas hydrate reservoir, and obtain the dynamic distribution of the natural gas hydrate decomposition interface and the hydrate decomposition rate in the reservoir.
Description
Technical Field
The invention relates to an evaluation device and an experimental method of a drilling fluid additive for phase stability of a natural gas hydrate, and belongs to the technical field of development of natural gas hydrates.
Background
The natural gas hydrate is a crystalline substance formed by natural gas and water under the conditions of high pressure and low temperature, the total amount of global natural gas hydrate resources is about twice of the total amount of traditional fossil energy, more than 90 percent of the global natural gas hydrate resources are distributed in the sea area, the natural gas hydrate resource amount of the sea area in China is about 800 million tons of oil equivalent, and the natural gas hydrate is an important potential high-efficiency clean oil-gas replacing energy. In recent years, natural gas hydrate mining technical research is developed in Russia, America, Japan, Canada and other developed countries, and deep water natural gas hydrate trial mining in south China and Hozio sea area also makes an important breakthrough, but all the natural gas hydrate trial mining methods are far away from commercial mining methods.
The natural gas hydrate is extremely sensitive to temperature and pressure, in the drilling process, a wellbore working fluid and the natural gas hydrate are subjected to a thermalization reaction, and the natural gas hydrate in a reservoir stratum is decomposed due to inappropriate drilling and completion parameters such as chemical characteristics of a drilling fluid filtrate, circulation temperature, discharge capacity and the like, so that the reservoir stratum structure is damaged, the well wall is unstable, the well is difficult to form and the like, and drilling exploration of wells with complex structures such as horizontal wells is particularly serious. The method has the advantages that the mechanism of stabilizing the phase state of the drilling fluid additive to the natural gas hydrate is clarified, the mechanism of stabilizing the phase state of the drilling fluid additive to the natural gas hydrate is quantitatively represented, and the method is key for ensuring the stability of a well wall in the drilling process of a hydrate reservoir stratum. At present, under the influence of temperature, pressure and chemical agents, the mechanism of action of the drilling fluid additive on the phase state stabilization of the natural gas hydrate is quite complex, test data is fresh, and the well wall stabilization mechanism does not have a systematic explanation, so that the drilling fluid additive becomes a difficult point in the field of natural gas hydrate drilling research.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides the device for evaluating the phase stability of the natural gas hydrate by the drilling fluid additive, which is used for rapidly measuring the influence degree of different drilling fluid additives on the phase state of the reservoir natural gas hydrate, further systematically analyzing the mechanism of the action of the drilling fluid additive on the phase stability of the natural gas hydrate, and providing an experimental basis for the system design and theoretical research of the natural gas hydrate drilling fluid.
The invention also provides an experimental method for evaluating the phase stability of the drilling fluid additive to the natural gas hydrate.
The technical scheme of the invention is as follows:
an evaluation device of a drilling fluid additive for phase stability of a natural gas hydrate comprises a gas injection system, a liquid injection system, a vacuumizing system, a natural gas hydrate simulated reservoir system, a reservoir permeability measurement system, a drilling fluid circulating system, a natural gas hydrate simulated reservoir temperature and pressure monitoring system and a reaction kettle temperature control system;
the gas injection system is used for injecting gas into the natural gas hydrate simulated reservoir and providing a gas source for the generation of the natural gas hydrate; the liquid injection system is used for injecting water into the natural gas hydrate simulated reservoir to provide a water source for the generation of the natural gas hydrate; the vacuumizing system is used for vacuumizing the reaction kettle and the pipeline so as to ensure the purity of the natural gas hydrate in the preparation process of the simulated reservoir; the natural gas hydrate simulated reservoir system is used for simulating a natural gas hydrate reservoir and providing a stable pressure environment for the reservoir; the reservoir permeability measurement system is used for measuring the permeability of the natural gas hydrate simulation reservoir; the drilling fluid circulating system is used for providing a closed circulating loop under high pressure for the drilling fluid; the natural gas hydrate simulated reservoir temperature and pressure monitoring system is used for accurately monitoring and collecting the temperature and pressure change in the reservoir in the drilling process in real time; the reaction kettle temperature control system is used for providing a stable temperature environment for the reaction kettle.
Preferably, the gas injection system comprises a natural gas source, wherein the natural gas source is connected with a fifth valve, a first pipeline, a gas booster pump, a sixth valve, a second gas storage tank, a second gas flowmeter, a seventh valve, the first valve, a natural gas hydrate reservoir fluid injection first pipeline group and a natural gas hydrate reservoir fluid injection second pipeline group sequentially through pipelines;
the natural gas source is used for providing natural gas required by a natural gas hydrate generation experiment, the gas booster pump is used for boosting the natural gas to meet the experiment pressure requirement, the second gas storage tank is used for storing the boosted natural gas, and the second gas flowmeter is used for measuring the flow rate of the natural gas flowing into the pipeline in real time; injecting fluid of a natural gas hydrate reservoir into the first pipeline group and injecting fluid of the natural gas hydrate reservoir into the second pipeline group to place two groups of same pipelines in a natural gas hydrate simulation reaction kettle before preparing the natural gas hydrate simulation reservoir;
further preferably, the second gas storage tank volume 40L.
Preferably, the length of the first pipeline set for injecting the natural gas hydrate reservoir fluid and the length of the second pipeline set for injecting the natural gas hydrate reservoir fluid in the natural gas hydrate simulation reaction kettle are both 1.5m, and each set comprises 28 air outlets with the length of 5mm and the diameter of 2mm and evenly distributed on the two sides of the pipeline; and the natural gas enters the first pipeline through the fifth valve, and enters the gas injection system through the seventh valve and the first valve after pressurization.
Preferably, the liquid injection system comprises a liquid storage tank, and the liquid storage tank is connected with a first liquid high-pressure pump, a first liquid flow meter, an eighth valve, a first pipeline group for injecting the natural gas hydrate reservoir fluid and a second pipeline group for injecting the natural gas hydrate reservoir fluid sequentially through pipelines;
the liquid storage tank is used for providing water required by a natural gas hydrate generation experiment, the first liquid high-pressure pump is used for providing power for the liquid in the storage tank to flow in a pipeline, and the first liquid flow meter is used for measuring the liquid flow in the inflow pipeline in real time; the gas injection system and the liquid injection system share the first pipeline set for natural gas hydrate reservoir fluid injection and the second pipeline set for natural gas hydrate reservoir fluid injection; the gas injection system and the liquid injection system can not work simultaneously, the seventh valve and the ninth valve need to be closed when the liquid injection system is started, water required by natural gas hydrate synthesis enters the second pipeline through the eighth valve, and enters the liquid injection system through the first valve through the first liquid high-pressure pump.
Preferably, the vacuumizing system comprises an emptying pipeline, a vacuum pump and a ninth valve which are sequentially connected through pipelines; and after the natural gas hydrate simulation reaction kettle is filled with sand, the vacuum pump is used for discharging gas in the reaction kettle and the pipeline from the ninth valve to the emptying pipeline.
Preferably, the natural gas hydrate simulated reservoir system comprises: the system comprises a natural gas hydrate simulation reaction kettle, a natural gas hydrate simulation reservoir and an electric elevator; the natural gas hydrate simulation reservoir is pre-filled into the natural gas hydrate simulation reaction kettle through a sand sample and used for simulating an actual natural gas hydrate reservoir, one end of the lifting machine is fixed to the upper portion of the constant temperature box, the other end of the lifting machine is connected with the natural gas hydrate simulation reaction kettle, and the natural gas hydrate simulation reaction kettle is lifted electrically to facilitate disassembly and sand sample pre-filling operation.
Preferably, the reservoir permeability measurement system comprises: the system comprises a nitrogen gas source, a second valve, a first pipeline, a third valve, a first gas storage tank, a first gas flowmeter, a fourth valve, a second pipeline, a first valve, a natural gas hydrate reservoir fluid injection first pipeline group, a natural gas hydrate reservoir fluid injection second pipeline group, a third pipeline, a back pressure valve, a third gas flowmeter and a first gas metering storage tank which are sequentially connected through pipelines;
after the preparation of the natural gas hydrate simulation reservoir is completed, the reservoir permeability measurement is started, a nitrogen gas source provides gas required by a permeability measurement experiment, a gas booster pump is used for boosting the pressure of the nitrogen gas so as to meet the experimental pressure requirement, a first gas storage tank is used for storing the nitrogen gas after the pressurization, a first gas flowmeter is used for measuring the nitrogen gas flow in an inflow pipeline in real time, a back pressure valve is used for adjusting the outlet pressure of a natural gas hydrate simulation reaction kettle, a third gas flowmeter is used for measuring the outlet nitrogen gas flow of the natural gas hydrate simulation reaction kettle in real time, and a first gas metering storage tank is used for storing nitrogen gas flowing out of the outlet of the natural gas hydrate simulation reaction kettle and displaying the pressure.
Further preferably, the first gas storage tank volume 40L.
Preferably, the drilling fluid circulating system comprises a chemical agent metering pump, and the chemical agent metering pump is sequentially connected with a tenth valve, a drilling fluid storage tank, a second liquid flowmeter, a gas-liquid separator, a second liquid high-pressure pump, a first high-pressure hose, a horizontal loading device, a conversion joint, a drilling machine, a drill rod, a high-pressure seal bearing, a customized drill bit, a built-in sleeve, a second high-pressure hose, a liquid-solid separator, a fifth pipeline, a sixth pipeline and an eleventh valve;
the chemical agent metering pump is used for pumping chemical additives for drilling fluid into a drilling fluid storage pool and metering the addition amount of the chemical agents in real time, the drilling fluid storage pool is used for storing and sealing the drilling fluid in a drilling fluid circulating system, the second liquid flow meter is used for metering the flow rate of the drilling fluid in a circulating pipeline in real time, the gas-liquid separator is used for separating gas in the drilling fluid, the second liquid high-pressure pump provides power for the circulating system, the first high-pressure hose is connected with the horizontal second liquid high-pressure pump and a drill rod and is high-pressure resistant and bendable, the loading device applies horizontal load to the drill rod through gear transmission, the conversion joint is used for being connected with the horizontal loading device and the drill rig to realize one-end loading and one-end rotation, the drill rig provides rotary power for the drill rod, the drill rod provides a flow, the customized drill bit is used for drilling a natural gas hydrate simulated reservoir, the built-in sleeve provides a flow channel for drilling fluid returned by the customized drill bit, the length of the built-in sleeve is 0.5m, the diameter of the built-in sleeve is 100mm, the built-in sleeve is preset in a natural gas hydrate simulated reaction kettle in advance, the liquid-solid separator is used for separating solids in the drilling fluid, the fourth gas flowmeter is used for metering gas separated by the gas-liquid separator, the second gas metering storage tank is used for storing gas separated by the weather-liquid separator and displaying a pressure value in real time, and the second high-pressure hose is used for connecting the built-in sleeve and drilling fluid returned by the drill pipe annulus.
Further preferably, the volume of the drilling fluid storage pool is 2m3The length of the drill rod is 1.6m, the diameter of the drill rod is 50mm, and the length of the built-in casing pipe is 0.5m, and the diameter of the built-in casing pipe is 100 mm.
Preferably, the system for monitoring temperature and pressure of the natural gas hydrate simulated reservoir comprises: the temperature and pressure sensor fixing device comprises a temperature and pressure sensor fixing rod, a temperature and pressure sensor, a data signal transmission line and a data processing system; a temperature and pressure sensor access port is reserved in the natural gas hydrate simulation reaction kettle, a temperature and pressure sensor fixer is used for fixing a sensor fixing rod, and the sensor fixing rod is used for connecting a first temperature and pressure sensor, a second temperature and pressure sensor and a third temperature and pressure sensor; the temperature and pressure sensor comprises a first temperature and pressure sensor, a second temperature and pressure sensor and a third temperature and pressure sensor and is used for monitoring the temperature and pressure change of the natural gas hydrate simulated reservoir in real time; the data signal transmission line is used for transmitting temperature and pressure data monitored by the temperature and pressure sensor, and the data processing system calculates, arranges and judges the natural gas hydrate phase states of different positions of the natural gas hydrate simulation reaction kettle.
Further preferably, the number of the temperature and pressure sensors is 16 and 48; the first temperature and pressure sensors are positioned 75mm away from the central axis of the natural gas hydrate simulated reaction kettle, 4 temperature and pressure sensors are uniformly arranged in the circumferential direction, and 16 temperature and pressure sensors are respectively arranged in 4 groups with the same axial distance of 0.55m, 0.80m, 1.05m and 1.3m away from the inlet section of the natural gas hydrate simulated reaction kettle; the second temperature and pressure sensors are located at a position 100mm away from the central axis of the natural gas hydrate simulated reaction kettle, 4 temperature and pressure sensors are uniformly arranged in the circumferential direction, and 16 temperature and pressure sensors are respectively arranged in 4 groups with the same axial distance of 0.55m, 0.80m, 1.05m and 1.3m from the inlet section of the natural gas hydrate simulated reaction kettle; the third temperature and pressure sensors are located at a position 125mm away from the central axis of the natural gas hydrate simulated reaction kettle, 4 sensors are uniformly arranged in the circumferential direction, and 16 sensors are respectively arranged at equal distances of 0.55m, 0.80m, 1.05m and 1.3m from the inlet section of the natural gas hydrate simulated reaction kettle in the axial direction, wherein the equal distances are 4 groups.
Preferably, reation kettle temperature control system includes thermostated container, thermostated container temperature control device, and the thermostated container is used for providing the required invariable temperature of experiment for natural gas hydrate simulation reation kettle, and thermostated container temperature control device is used for real-time regulation and accurate control thermostated container temperature.
Further preferably, the temperature control range of the incubator is 0-100 ℃.
In a closed loop, all parts and pipelines are resistant to pressure of 40MPa, and the method can be used for experimental evaluation of the phase stability of the drilling fluid additive to the natural gas hydrate.
The experimental method for evaluating the phase stability of the drilling fluid additive to the natural gas hydrate adopts the experimental device, and comprises the following steps:
(1) and manufacturing the natural gas hydrate simulation reservoir
Pre-filling a sand sample into a natural gas hydrate simulation reaction kettle according to experimental design requirements, adjusting a second valve, a third valve, a fourth valve, a fifth valve, a sixth valve, a seventh valve, an eighth valve and a back pressure valve to be in a closed state after filling is finished, and opening a ninth valve and a first valve to remove air in an experimental pipeline by using a vacuum pump; closing the ninth valve, opening the fifth valve, the sixth valve and the seventh valve, and setting the total amount of injected natural gas according to the saturation of the natural gas hydrate; closing the fifth valve, the sixth valve and the seventh valve, opening the eighth valve, and setting the total amount of the injected clear water liquid according to the saturation of the natural gas hydrate;
(2) gas hydrate simulated reservoir permeability measurement
Adjusting the fifth valve, the sixth valve, the seventh valve, the eighth valve and the ninth valve to be in a closed state, opening the second valve, the third valve, the fourth valve and the back pressure valve, allowing nitrogen to flow into the natural gas hydrate simulated reservoir under the action of the gas booster pump, and measuring the permeability of the natural gas hydrate simulated reservoir after the parameters are stable; preferably, after the parameters have stabilized, the first gas reservoir pressure p is read1The pressure p of the first gas metering storage tank2Gas flow Q of the third gas flowmeter0And calculating the permeability of the natural gas hydrate simulated reservoir:
in the formula, kgPermeability, m, of a simulated reservoir of natural gas hydrate2；p1Inlet first gas storage tank pressure, Pa; p is a radical of2Metering the storage tank pressure, Pa, p, for the first gas at the outlet0Atmospheric pressure, Pa; mu is dynamic viscosity of nitrogen gas, Pa.s; q0Is the volume flow of gas at atmospheric pressure, m3And/s, A is the cross-sectional area of the simulated reservoir of the natural gas hydrate, and m2(ii) a L is the length of the natural gas hydrate simulated reservoir, m;
(3) evaluation experiment of drilling fluid additive on natural gas hydrate phase stability
Adjusting the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the sixth valve, the seventh valve, the eighth valve, the ninth valve, the tenth valve and the back pressure valve to be in a closed state, adjusting the temperature and the pressure of an experimental system to be the temperature and the pressure set by the experiment, opening the eleventh valve, starting the second liquid high-pressure pump, the horizontal loading device and the drilling machine, adding conventional drilling fluid into a drilling fluid storage pool, performing a drilling circulation drilling experiment without drilling fluid additives, and performing dynamic distribution and hydrate decomposition rate of a natural gas hydrate decomposition interface in a simulated reservoir without drilling fluid additives;
preferably, a drilling circulation drilling experiment is carried out without the drilling fluid additive, the temperature and pressure changes at different positions in the natural gas hydrate simulated reservoir 41 are monitored in real time by the first temperature sensor 331, the second temperature sensor 332, the third temperature sensor 333 and the pressure sensor 333, and the temperatures T at different positions are measurediPressure piComparing the data with the natural gas hydrate phase state curve model, judging whether the natural gas hydrate at the position is decomposed or not, and measuring the decomposition rate v of the natural gas hydrate in real time by the fourth gas flowmeter 223iThe natural gas hydrate phase curve model is as follows:
in the above formula, T is the system temperature, K; Δ μ0Is the chemical potential difference between the empty hydrate crystal lattice and water in pure water in a standard state; t is0Is the temperature in the standard state, K; p is a radical of0Is the pressure at standard conditions, Pa; Δ H0Is the specific enthalpy difference between the empty hydrate crystal lattice and pure water, J/kg; Δ V is the specific volume difference between the empty hydrate lattice and pure water, m3/kg；ΔCpThe specific heat tolerance of the empty hydrate crystal lattice and pure water is J/(kg. K); r is a gas constant of 8.314J/(mol.K); n is a radical ofcThe number of components in the mixture which can generate hydrate; epsiloniThe number of i-type holes in unit water molecule in the hydrate phase; thetaijThe occupancy ratio of the guest molecule j in the i-shaped hole; f. ofwPa is the fugacity of water in the water-rich phase;
pa is the fugacity of pure water at reference states T and p. If the type of hydrate, constant θijAnd CijCan be determined; meanwhile, the concentration of the drilling fluid additive can be obtained according to experimental measurement
Numerical values.
The dynamic distribution B of the natural gas hydrate decomposition interface in the simulated reservoir 41 of the natural gas hydrate drilled by the horizontal well without the drilling fluid additive can be derived in real time through the data processing system 35m,tAnd rate of hydrate decomposition vm,t。
And (3) repeating the step (1) and the step (2) by using an experimental device shown in the figure 1, starting a chemical agent metering pump and a tenth valve, pumping a drilling fluid additive with a set concentration into a drilling fluid storage pool, and continuously repeating the step (3) to measure and obtain the dynamic distribution of the natural gas hydrate decomposition interface and the hydrate decomposition rate in the simulated reservoir stratum of the natural gas hydrate drilled by the horizontal well containing the drilling fluid additive with the set concentration.
By comparing B at different positions and different timesm,tAnd Bm,t、vm,tAnd vn,tThe method can evaluate the influence degree of the drilling fluid additive on the phase state stability of the natural gas hydrate in the reservoir under the drilling condition, change the discharge capacity of the drilling fluid and the concentration of the additive, draw a distribution chart of the drilling fluid additive on the natural gas hydrate decomposition interface in the reservoir along with the change of the discharge capacity of the drilling fluid and the concentration of the additive, and provide an experimental basis for the optimization of the drilling fluid additive.
The invention has the beneficial effects that:
(1) the method can simulate the drilling condition of a real horizontal well, realize the real-time measurement of the influence range of the drilling fluid additive in the natural gas hydrate reservoir, and obtain the dynamic distribution of the natural gas hydrate decomposition interface and the hydrate decomposition rate in the reservoir.
(2) The device is easy to operate and high in feasibility.
(3) The measuring method is scientific, and can realize high-precision parameter measurement.
Drawings
FIG. 1 is an apparatus for evaluating the phase stability of a drilling fluid additive to natural gas hydrates;
FIG. 2 is a layout diagram of the equipment inside the controllable incubator;
FIG. 3 is a cross-sectional layout diagram of temperature and pressure sensors in a reaction kettle;
in the figure: 101. a first pipeline; 102. a second pipeline; 103. a first valve; 104. injecting natural gas hydrate reservoir fluid into the first pipeline set; 105. injecting natural gas hydrate reservoir fluid into the second pipeline set; 111. a nitrogen source; 112. a second valve; 113. a third valve; 114. a first gas storage tank; 115. a first gas flow meter; 116. a fourth valve; 121. a natural gas source; 122. a fifth valve; 123. a sixth valve; 124. a second gas storage tank; 125. a second gas flow meter; 126. a seventh valve; 131. a liquid storage tank; 132. a first high-pressure liquid pump; 133. a first liquid flow meter; 134. an eighth valve; 14. a gas booster pump; 141. an emptying pipeline; 142. a vacuum pump; 143. a ninth valve; 151. a third pipeline; 152. a back pressure valve; 153. a third gas flow meter; 154. a first gas metering storage tank; 201. a chemical agent metering pump; 202. a tenth valve; 203. a drilling fluid storage pool; 204. a second liquid flow meter; 205. a gas-liquid separator; 206. a second liquid high-pressure pump; 207. a first high pressure hose; 208. a horizontal loading device; 209. a crossover sub; 210. a drilling machine; 211. a drill stem; 212. a high pressure seal bearing; 213. customizing a drill bit; 214. a sleeve is arranged inside; 215. a second high pressure hose; 216. a liquid-solid separator; 217. a fifth pipeline; 221. a sixth pipeline; 222. an eleventh valve; 223. a fourth gas flow meter; 224. a second gas metering storage tank; 3. a natural gas hydrate simulated reservoir temperature and pressure monitoring system; 31. a temperature pressure sensor holder; 32. a sensor fixing rod; 33. a temperature pressure sensor; 331. a first temperature pressure sensor; 332. a second temperature and pressure sensor; 333. a third temperature and pressure sensor; 34. a data signal transmission line; 35. a data processing system; 4. a natural gas hydrate simulation reaction kettle; 41. simulating a reservoir with a natural gas hydrate; 42. an electric hoist; 5. a thermostat; 51. thermostat temperature control device.
Detailed Description
The present invention will be further described by way of examples, but not limited thereto, with reference to the accompanying drawings.
Example 1:
as shown in fig. 1, an evaluation device of a drilling fluid additive for natural gas hydrate phase stability includes a gas injection system, a liquid injection system, a vacuum pumping system, a natural gas hydrate simulated reservoir system, a reservoir permeability measurement system, a drilling fluid circulation system, a natural gas hydrate simulated reservoir temperature, a pressure monitoring system, and a reaction kettle temperature control system. The gas injection system injects gas into the natural gas hydrate simulated reservoir to provide a gas source for the generation of the natural gas hydrate; the liquid injection system injects water into the natural gas hydrate simulation reservoir to provide a water source for the generation of the natural gas hydrate; the vacuumizing system is used for vacuumizing the reaction kettle and the pipeline so as to ensure the purity of the natural gas hydrate in the preparation process of the simulated reservoir; the natural gas hydrate simulated reservoir system is a simulated natural gas hydrate reservoir and provides a stable pressure environment for the reservoir; the reservoir permeability measurement system is used for measuring the permeability of the natural gas hydrate simulated reservoir; the drilling fluid circulating system provides a closed circulating loop under high pressure for the drilling fluid; the natural gas hydrate simulated reservoir temperature and pressure monitoring system accurately monitors and collects the temperature and pressure changes in the reservoir in the drilling process in real time; the reaction kettle temperature control system provides a stable temperature environment for the reaction kettle.
A gas injection system, comprising: a natural gas source 121, a fifth valve 122, a first pipeline 101, a gas booster pump 14, a sixth valve 123, a second gas storage tank 124, a second gas flow meter 125, a seventh valve 126, a first valve 103, a natural gas hydrate reservoir fluid injection first pipeline set 104, and a natural gas hydrate reservoir fluid injection second pipeline set 105 are sequentially connected by pipelines; the natural gas source 121 provides natural gas required by a natural gas hydrate generation experiment, the gas booster pump 14 boosts the natural gas to meet the experiment pressure requirement, the second gas storage tank 124 is used for storing the boosted natural gas and the volume is 40L, and the second gas flowmeter 125 is used for measuring the flow rate of the natural gas flowing into a pipeline in real time; injecting a natural gas hydrate reservoir fluid into the first pipeline group 104 and injecting a natural gas hydrate reservoir fluid into the second pipeline group 105 to place two groups of identical pipelines in the natural gas hydrate simulation reaction kettle 4 before preparing the natural gas hydrate simulation reservoir, wherein the lengths of the first pipeline group 104 and the second pipeline group 105 in the natural gas hydrate simulation reaction kettle 4 are both 1.5m, and each group comprises 28 air outlets with the lengths of 5mm and the diameters of 2mm and are uniformly distributed on two sides of the pipelines; natural gas enters the first pipeline 101 through the fifth valve 122, and enters the gas injection system through the seventh valve 126 and the first valve 103 after pressurization.
A liquid injection system comprising: the liquid storage tank 131, the first high-pressure liquid pump 132, the first liquid flow meter 133, the eighth valve 134, the first valve 103, the first gas hydrate reservoir fluid injection pipeline group 104, and the second gas hydrate reservoir fluid injection pipeline group 105 are sequentially connected by pipelines; the liquid storage tank 131 provides water required by natural gas hydrate generation experiments, the first high-pressure liquid pump 132 provides power for liquid in the storage tank to flow in a pipeline, and the first liquid flow meter 133 is used for measuring the liquid flow in the inflow pipeline in real time; the gas injection system and the liquid injection system share a natural gas hydrate reservoir fluid injection first line set 104 and a natural gas hydrate reservoir fluid injection second line set 105; the gas injection system and the liquid injection system cannot work simultaneously, the seventh valve 126 and the ninth valve 143 need to be closed when the liquid injection system is started, and water required for natural gas hydrate synthesis enters the second pipeline 102 through the eighth valve 134 and enters the liquid injection system through the first valve 103 through the first high-pressure liquid pump 132.
An evacuation system comprising: the emptying pipeline 141, the vacuum pump 142 and the ninth valve 143 are connected in sequence through pipelines; after the natural gas hydrate simulation reaction kettle 4 is filled with sand, the vacuum pump 142 discharges the gas in the reaction kettle and the pipeline from the ninth valve 143 to the vent pipeline 141.
A gas hydrate simulated reservoir system comprising: the system comprises a natural gas hydrate simulation reaction kettle 4, a natural gas hydrate simulation reservoir 41 and an electric elevator 42; the natural gas hydrate simulation reservoir 41 is pre-filled into the natural gas hydrate simulation reaction kettle 4 through a sand sample and used for simulating an actual natural gas hydrate reservoir, one end of the lifting machine 42 is fixed to the upper portion of the constant temperature box 5, the other end of the lifting machine is connected with the natural gas hydrate simulation reaction kettle 4, and the natural gas hydrate simulation reaction kettle 4 is lifted electrically to facilitate disassembly and sand sample pre-filling operation.
A reservoir permeability measurement system comprising: the system comprises a nitrogen gas source 111, a second valve 112, a first pipeline 101, a third valve 113, a first gas storage tank 114, a first gas flow meter 115, a fourth valve 116, a second pipeline 102, a first valve 103, a natural gas hydrate reservoir fluid injection first pipeline set 104, a natural gas hydrate reservoir fluid injection second pipeline set 105, a third pipeline 151, a back pressure valve 152, a third gas flow meter 153 and a first gas metering storage tank 154 which are sequentially connected through pipelines; after the preparation of the natural gas hydrate simulation reservoir 41 is completed, the reservoir permeability measurement is started, the nitrogen gas source 121 provides gas required by a permeability measurement experiment, the gas booster pump 14 boosts the nitrogen gas to meet the experiment pressure requirement, the first gas storage tank 114 is used for storing the boosted nitrogen gas and has a volume of 40L, the first gas flowmeter 115 is used for measuring the nitrogen flow in the inflow pipeline in real time, the back pressure valve 152 is used for adjusting the outlet pressure of the natural gas hydrate simulation reaction kettle 4, the third gas flowmeter 153 is used for measuring the outlet nitrogen flow of the natural gas hydrate simulation reaction kettle 4 in real time, and the first gas metering storage tank 154 is used for storing the nitrogen gas flowing out from the outlet of the natural gas hydrate simulation reaction kettle 4 and displaying the pressure value in real time.
A drilling fluid circulation system comprising: a chemical agent metering pump 201, a tenth valve 202, a drilling fluid storage tank 203, a second liquid flow meter 204, a gas-liquid separator 205, a second liquid high-pressure pump 206, a first high-pressure hose 207, a horizontal loading device 208, a conversion joint 209, a drilling rig 210, a drill pipe 211, a high-pressure seal bearing 212, a customized drill bit 213, an internal casing 214, a second high-pressure hose 215, a liquid-solid separator 216, a fifth pipeline 217, a sixth pipeline 221, an eleventh valve 222; the chemical agent metering pump 201 is used for pumping chemical additives for drilling fluid into the drilling fluid storage tank 203 and metering the addition amount of the chemical agents in real time, and the drilling fluid storage tank 203 is used for storing and sealing the drilling fluid in the drilling fluid circulating system and has the volume of 2m3The second liquid flowmeter 204 is used for measuring the flow of drilling fluid in a circulating pipeline in real time, the gas-liquid separator 205 is used for separating gas in the drilling fluid, the second liquid high-pressure pump 206 is used for providing power for the circulating system, the first high-pressure hose 207 is connected with the horizontal second liquid high-pressure pump 206 and a drill pipe 211, is high-pressure resistant and bendable, and the loading device 208 transmits the drilling fluid through a gearDynamically applying a horizontal load to a drill rod 211, connecting a conversion joint 209 with a horizontal loading device 208 and a drilling machine 210 to realize one-end loading and one-end rotation, wherein the drilling machine 210 provides a rotation power for the drill rod 211, the drill rod 211 provides a flow channel for drilling fluid and applies a bit pressure to a custom drill bit 213, the length of the drill rod is 1.6m, the diameter of the drill rod is 50mm, a high-pressure seal bearing 212 is used for high-pressure dynamic seal of the drill rod 211 and the natural gas hydrate simulation reaction kettle 4, the custom drill bit 213 is used for drilling the natural gas hydrate simulation reservoir 41, a built-in sleeve 214 provides a flow channel for the custom drill bit 213 to return the drilling fluid, the length of the drill bit is 0.5m, the diameter of the drill bit is 100mm, the natural gas hydrate simulation reaction kettle 4 is preset in advance, a liquid-solid separator 216 is used for separating solids in the drilling fluid, a fourth gas flowmeter 223 is used for metering, the second high-pressure hose 215 is used for connecting the built-in casing 214 with the drilling fluid returned from the annulus of the drill pipe 211, flowing into the liquid-solid separator 216, and being resistant to high pressure and capable of bending.
The natural gas hydrate simulation reservoir temperature, pressure monitoring system 3 includes: a temperature and pressure sensor holder 31, a sensor fixing rod 32, a temperature and pressure sensor 33, a data signal transmission line 34, a data processing system 35; a temperature and pressure sensor 33 access port is reserved in the natural gas hydrate simulation reaction kettle 4, the temperature and pressure sensor fixer 31 is used for fixing a sensor fixing rod, and the sensor fixing rod is used for connecting a first temperature and pressure sensor 331, a second temperature and pressure sensor 332 and a third temperature and pressure sensor 333; the temperature and pressure sensors 33 comprise a first temperature and pressure sensor 331, a second temperature and pressure sensor 332 and a third temperature and pressure sensor 333, and are used for monitoring the temperature and pressure changes of the natural gas hydrate simulated reservoir 41 in real time, and 16 sets of 48 sensors are used; the first temperature and pressure sensors 331 are located 75mm away from the central axis of the natural gas hydrate simulated reaction kettle 4, 4 sensors are uniformly arranged in the circumferential direction, and 16 sensors are respectively arranged in 4 groups with the same axial distance of 0.55m, 0.80m, 1.05m and 1.3m away from the inlet section of the natural gas hydrate simulated reaction kettle 4; the second temperature and pressure sensors 332 are positioned at a position 100mm away from the central axis of the natural gas hydrate simulated reaction kettle 4, 4 sensors are uniformly arranged in the circumferential direction, and 16 sensors are respectively arranged in 4 groups with the same axial distance of 0.55m, 0.80m, 1.05m and 1.3m from the inlet section of the natural gas hydrate simulated reaction kettle 4; the third temperature and pressure sensors 333 are positioned at 125mm away from the central axis of the natural gas hydrate simulated reaction kettle 4, 4 sensors are uniformly arranged in the circumferential direction, and 16 sensors are respectively arranged in 4 groups with the same axial distance of 0.55m, 0.80m, 1.05m and 1.3m from the inlet section of the natural gas hydrate simulated reaction kettle 4; the data signal transmission line 34 is used for transmitting temperature and pressure data monitored by the pressure sensor 33, and the data processing system 35 calculates, collates and judges the natural gas hydrate phase states at different positions of the natural gas hydrate simulation reaction kettle 4 according to the temperature and pressure data.
The reaction kettle temperature control system comprises a thermostat 5 and a thermostat temperature control device 51, wherein the thermostat 5 natural gas hydrate simulation reaction kettle 4 provides constant temperature and a temperature control range of 0-100 ℃ required by an experiment, and the thermostat temperature control device 51 can adjust and accurately control the temperature of the thermostat 5 in real time.
In a closed loop, all parts and pipelines are resistant to pressure of 40MPa, and the method can be used for experimental evaluation of the phase stability of the drilling fluid additive to the natural gas hydrate.
Example 2
The experiment for evaluating the phase stability of the drilling fluid additive to the natural gas hydrate by using the device in the embodiment 1 mainly comprises the following steps:
(1) and manufacturing the natural gas hydrate simulation reservoir
According to the experimental design requirements, sand samples are pre-filled into the natural gas hydrate simulation reaction kettle 4, after filling is finished, the second valve 112, the third valve 113, the fourth valve 116, the fifth valve 122, the sixth valve 123, the seventh valve 126, the eighth valve 134 and the back pressure valve 152 are adjusted to be in a closed state, and the ninth valve 143 and the first valve 103 are opened to remove air in an experimental pipeline by using a vacuum pump; closing the ninth valve 143, opening the fifth valve 122, the sixth valve 123 and the seventh valve 126, and setting the total amount of the injected natural gas according to the saturation degree of the natural gas hydrate; closing the fifth valve 122, the sixth valve 123 and the seventh valve 126, opening the eighth valve 134, and setting the total amount of the injected clear water liquid according to the saturation degree of the natural gas hydrate; if the saturation of the natural gas hydrate does not meet the experimental requirement, the injection of the natural gas and the clean water needs to be carried out repeatedly for many times.
(2) Gas hydrate simulated reservoir permeability measurement
Adjusting the fifth valve 122, the sixth valve 123, the seventh valve 126, the eighth valve 134 and the ninth valve 143 to be in a closed state, opening the second valve 112, the third valve 113, the fourth valve 116 and the backpressure valve 152, allowing nitrogen to flow into the gas hydrate simulated reservoir 41 under the action of the gas booster pump 14, and reading the pressure p of the first gas storage tank after the parameters are stable1The pressure p of the first gas metering storage tank2Gas flow Q of the third gas flowmeter0And calculating the permeability of the natural gas hydrate simulated reservoir:
in the formula, kgPermeability, m, of a simulated reservoir of natural gas hydrate2；p1Inlet first gas storage tank pressure, Pa; p is a radical of2Metering the storage tank pressure, Pa, p, for the first gas at the outlet0Atmospheric pressure, Pa; mu is dynamic viscosity of nitrogen gas, Pa.s; q0Is the volume flow of gas at atmospheric pressure, m3And/s, A is the cross-sectional area of the simulated reservoir of the natural gas hydrate, and m2(ii) a And L is the length of the natural gas hydrate simulated reservoir, m.
(3) Evaluation experiment of drilling fluid additive on natural gas hydrate phase stability
Adjusting the first valve 103, the second valve 112, the third valve 113, the fourth valve 116, the fifth valve 122, the sixth valve 123, the seventh valve 126, the eighth valve 134, the ninth valve 143, the tenth valve 202 and the back pressure valve 152 to be in a closed state, adjusting the temperature and the pressure of the experimental system to be the temperature T and the pressure p set by the experiment, opening the eleventh valve 222, starting the second liquid high-pressure pump 206, the horizontal loading device 208 and the drilling machine 210, adding the conventional drilling fluid into the drilling fluid storage tank 203, and performing the downward drilling without the drilling fluid additiveIn a well circulation drilling experiment, the first temperature and pressure sensor 331, the second temperature and pressure sensor 332, the third temperature and pressure sensor 333 monitor the temperature and pressure changes of different positions in the natural gas hydrate simulated reservoir 41 in real time, and the temperatures T of the different positions are measurediPressure piComparing the data with the natural gas hydrate phase state curve model, judging whether the natural gas hydrate at the position is decomposed or not, and measuring the decomposition rate v of the natural gas hydrate in real time by the fourth gas flowmeter 223iThe natural gas hydrate phase curve model is as follows:
in the above formula, T is the system temperature, K; Δ μ0Is the chemical potential difference between the empty hydrate crystal lattice and water in pure water in a standard state; t is0Is the temperature in the standard state, K; p is a radical of0Is the pressure at standard conditions, Pa; Δ H0Is the specific enthalpy difference between the empty hydrate crystal lattice and pure water, J/kg; Δ V is the specific volume difference between the empty hydrate lattice and pure water, m3/kg；ΔCpThe specific heat tolerance of the empty hydrate crystal lattice and pure water is J/(kg. K); r is a gas constant of 8.314J/(mol.K); n is a radical ofcThe number of components in the mixture which can generate hydrate; epsiloniThe number of i-type holes in unit water molecule in the hydrate phase; thetaijThe occupancy ratio of the guest molecule j in the i-shaped hole; f. ofwPa is the fugacity of water in the water-rich phase;
pa is the fugacity of pure water at reference states T and p. If the type of hydrate, constant θijAnd CijCan be determined; meanwhile, the concentration of the drilling fluid additive can be obtained according to experimental measurement
Numerical values.
The data processing system 35 can be used for real-time derivation of the simulation reservoir of the natural gas hydrate drilled by the horizontal well without the drilling fluid additiveDynamic distribution B of natural gas hydrate decomposition interface in 41m,tAnd rate of hydrate decomposition vm,t。
By using the experimental device shown in fig. 1, repeating the step (1) and the step (2), starting the chemical agent metering pump 201 and the tenth valve 202, pumping a drilling fluid additive with a set concentration into the drilling fluid storage pool 203, continuously repeating the step (3), and leading out the dynamic distribution B of the natural gas hydrate decomposition interface in the simulated reservoir 41, in which the horizontal well containing the drilling fluid additive with the set concentration drills the natural gas hydrate decomposition interface in real time through the data processing system 35n,tAnd rate of hydrate decomposition vn,t。
By comparing B at different positions and different timesm,tAnd Bm,t、vm,tAnd vn,tThe method can evaluate the influence degree of the drilling fluid additive on the phase state stability of the natural gas hydrate in the reservoir under the drilling condition, change the discharge capacity of the drilling fluid and the concentration of the additive, draw a distribution chart of the drilling fluid additive on the natural gas hydrate decomposition interface in the reservoir along with the change of the discharge capacity of the drilling fluid and the concentration of the additive, and provide an experimental basis for the optimization of the drilling fluid additive.
Claims (10)
1. The device for evaluating the phase stability of the natural gas hydrate by the drilling fluid additive is characterized by comprising a gas injection system, a liquid injection system, a vacuumizing system, a natural gas hydrate simulated reservoir system, a reservoir permeability measuring system, a drilling fluid circulating system, a natural gas hydrate simulated reservoir temperature and pressure monitoring system and a reaction kettle temperature control system;
the gas injection system is used for injecting gas into the natural gas hydrate simulated reservoir and providing a gas source for the generation of the natural gas hydrate; the liquid injection system is used for injecting water into the natural gas hydrate simulated reservoir to provide a water source for the generation of the natural gas hydrate; the vacuumizing system is used for vacuumizing the reaction kettle and the pipeline; the natural gas hydrate simulated reservoir system is used for simulating a natural gas hydrate reservoir and providing a pressure environment for the reservoir; the reservoir permeability measurement system is used for measuring the permeability of the natural gas hydrate simulation reservoir; the drilling fluid circulating system is used for providing a closed circulating loop under high pressure for the drilling fluid; the natural gas hydrate simulated reservoir temperature and pressure monitoring system is used for monitoring and acquiring the temperature and pressure change in the reservoir in the drilling process in real time; the reaction kettle temperature control system is used for providing a stable temperature environment for the reaction kettle.
2. The evaluation device of the phase stability of the natural gas hydrate by the drilling fluid additive according to claim 1, wherein the gas injection system comprises a natural gas source, and the natural gas source is connected with a fifth valve, a first pipeline, a gas booster pump, a sixth valve, a second gas storage tank, a second gas flowmeter, a seventh valve, the first valve, a first pipeline group for injecting the natural gas hydrate reservoir fluid and a second pipeline group for injecting the natural gas hydrate reservoir fluid sequentially through pipelines;
the natural gas source is used for providing natural gas required by a natural gas hydrate generation experiment, the gas booster pump is used for boosting the natural gas to meet the experiment pressure requirement, the second gas storage tank is used for storing the boosted natural gas, and the second gas flowmeter is used for measuring the flow rate of the natural gas flowing into the pipeline in real time; injecting fluid of a natural gas hydrate reservoir into the first pipeline group and injecting fluid of the natural gas hydrate reservoir into the second pipeline group to place two groups of same pipelines in a natural gas hydrate simulation reaction kettle before preparing the natural gas hydrate simulation reservoir;
preferably, the second gas storage tank volume 40L;
preferably, the length of the first pipeline set for injecting the natural gas hydrate reservoir fluid and the length of the second pipeline set for injecting the natural gas hydrate reservoir fluid in the natural gas hydrate simulation reaction kettle are both 1.5m, and each set comprises 28 air outlets with the length of 5mm and the diameter of 2mm and evenly distributed on the two sides of the pipeline; and the natural gas enters the first pipeline through the fifth valve, and enters the gas injection system through the seventh valve and the first valve after pressurization.
3. The device for evaluating the phase stability of the natural gas hydrate by the drilling fluid additive according to claim 2, wherein the liquid injection system comprises a liquid storage tank, and the liquid storage tank is connected with a first liquid high-pressure pump, a first liquid flow meter, an eighth valve, a first pipeline group for injecting the natural gas hydrate reservoir fluid and a second pipeline group for injecting the natural gas hydrate reservoir fluid sequentially through pipelines;
the liquid storage tank is used for providing water required by a natural gas hydrate generation experiment, the first liquid high-pressure pump is used for providing power for the liquid in the storage tank to flow in a pipeline, and the first liquid flow meter is used for measuring the liquid flow in the inflow pipeline in real time; the gas injection system and the liquid injection system share the first pipeline set for natural gas hydrate reservoir fluid injection and the second pipeline set for natural gas hydrate reservoir fluid injection; and water required by the synthesis of the natural gas hydrate enters the second pipeline through the eighth valve, passes through the first liquid high-pressure pump and enters the liquid injection system through the first valve.
4. The device for evaluating the phase stability of the natural gas hydrate by the drilling fluid additive according to claim 3, wherein the vacuumizing system comprises an emptying pipeline, a vacuum pump and a ninth valve which are sequentially connected through a pipeline; and after the natural gas hydrate simulation reaction kettle is filled with sand, the vacuum pump is used for discharging gas in the reaction kettle and the pipeline from the ninth valve to the emptying pipeline.
5. The evaluation device of the drilling fluid additive for evaluating the phase stability of the natural gas hydrate, according to claim 4, is characterized in that the natural gas hydrate simulated reservoir system comprises: the system comprises a natural gas hydrate simulation reaction kettle, a natural gas hydrate simulation reservoir and an electric elevator; the natural gas hydrate simulation reaction kettle is electrically lifted.
6. The evaluation device of the drilling fluid additive for the phase stability of the natural gas hydrate, according to claim 5, is characterized in that the reservoir permeability measurement system comprises: the system comprises a nitrogen gas source, a second valve, a first pipeline, a third valve, a first gas storage tank, a first gas flowmeter, a fourth valve, a second pipeline, a first valve, a natural gas hydrate reservoir fluid injection first pipeline group, a natural gas hydrate reservoir fluid injection second pipeline group, a third pipeline, a back pressure valve, a third gas flowmeter and a first gas metering storage tank which are sequentially connected through pipelines;
after the preparation of the natural gas hydrate simulation reservoir is finished, reservoir permeability measurement is started, a nitrogen gas source provides gas required by a permeability measurement experiment, a gas booster pump is used for boosting the nitrogen gas to meet the experiment pressure requirement, a first gas storage tank is used for storing the boosted nitrogen gas, a first gas flowmeter is used for measuring the nitrogen gas flow in a pipeline in real time, a back pressure valve is used for adjusting the outlet pressure of a natural gas hydrate simulation reaction kettle, a third gas flowmeter is used for measuring the nitrogen gas flow at the outlet of the natural gas hydrate simulation reaction kettle in real time, and a first gas metering storage tank is used for storing nitrogen gas flowing out of the outlet of the natural gas hydrate simulation reaction kettle and displaying the pressure value in real time;
preferably, the first gas storage tank volume 40L.
7. The device for evaluating the phase stability of the natural gas hydrate by the drilling fluid additive according to claim 6, wherein the drilling fluid circulating system comprises a chemical agent metering pump, and the chemical agent metering pump is sequentially connected with a tenth valve, a drilling fluid storage tank, a second liquid flow meter, a gas-liquid separator, a second liquid high-pressure pump, a first high-pressure hose, a horizontal loading device, a conversion joint, a drilling machine, a drill rod, a high-pressure sealed bearing, a customized drill bit, a built-in sleeve, a second high-pressure hose, a liquid-solid separator, a fifth pipeline, a sixth pipeline and an eleventh valve;
the chemical agent metering pump is used for pumping chemical additives for drilling fluid into a drilling fluid storage pool and metering the addition amount of the chemical agents in real time, the drilling fluid storage pool is used for storing and sealing the drilling fluid in a drilling fluid circulating system, the second liquid flow meter is used for metering the flow rate of the drilling fluid in a circulating pipeline in real time, the gas-liquid separator is used for separating gas in the drilling fluid, the second liquid high-pressure pump provides power for the circulating system, the first high-pressure hose is connected with the horizontal second liquid high-pressure pump and a drill rod, the loading device applies horizontal load to the drill rod through gear transmission, the conversion joint is used for connecting the horizontal loading device and a drilling machine, the drilling machine provides rotary power for the drill rod, the drill rod provides a flow channel for the drilling fluid and applies drilling pressure to a customized drill bit, the high-pressure seal bearing, the built-in sleeve pipe provides a flow channel for the drilling fluid returned by the customized drill bit, the liquid-solid separator is used for separating solids in the drilling fluid, the fourth gas flowmeter is used for metering gas separated by the gas-liquid separator, the second gas metering storage tank is used for storing the gas separated by the weather-liquid separator and displaying a pressure value in real time, and the second high-pressure hose is used for connecting the built-in sleeve pipe and the drilling fluid returned by the drill pipe annulus to flow into the liquid-solid separator;
preferably, the volume of the drilling fluid storage pool is 2m3The length of the drill rod is 1.6m, the diameter of the drill rod is 50mm, and the length of the built-in casing pipe is 0.5m, and the diameter of the built-in casing pipe is 100 mm.
8. The evaluation device of the drilling fluid additive for the phase stability of the natural gas hydrate, according to claim 7, is characterized in that the natural gas hydrate simulated reservoir temperature pressure monitoring system comprises: the temperature and pressure sensor fixing device comprises a temperature and pressure sensor fixing rod, a temperature and pressure sensor, a data signal transmission line and a data processing system; a temperature and pressure sensor access port is reserved in the natural gas hydrate simulation reaction kettle, a temperature and pressure sensor fixer is used for fixing a sensor fixing rod, and the sensor fixing rod is used for connecting a first temperature and pressure sensor, a second temperature and pressure sensor and a third temperature and pressure sensor; the temperature and pressure sensor comprises a first temperature and pressure sensor, a second temperature and pressure sensor and a third temperature and pressure sensor and is used for monitoring the temperature and pressure change of the natural gas hydrate simulated reservoir in real time; the data signal transmission line is used for transmitting temperature and pressure data monitored by the temperature and pressure sensor, and the data processing system calculates, collates and judges the natural gas hydrate phase states at different positions of the natural gas hydrate simulation reaction kettle;
preferably, the number of the temperature and pressure sensors is 16 and 48; the first temperature and pressure sensors are positioned 75mm away from the central axis of the natural gas hydrate simulated reaction kettle, 4 temperature and pressure sensors are uniformly arranged in the circumferential direction, and 16 temperature and pressure sensors are respectively arranged in 4 groups with the same axial distance of 0.55m, 0.80m, 1.05m and 1.3m away from the inlet section of the natural gas hydrate simulated reaction kettle; the second temperature and pressure sensors are located at a position 100mm away from the central axis of the natural gas hydrate simulated reaction kettle, 4 temperature and pressure sensors are uniformly arranged in the circumferential direction, and 16 temperature and pressure sensors are respectively arranged in 4 groups with the same axial distance of 0.55m, 0.80m, 1.05m and 1.3m from the inlet section of the natural gas hydrate simulated reaction kettle; the third temperature and pressure sensors are located at a position 125mm away from the central axis of the natural gas hydrate simulated reaction kettle, 4 sensors are uniformly arranged in the circumferential direction, and 16 sensors are respectively arranged at equal distances of 0.55m, 0.80m, 1.05m and 1.3m from the inlet section of the natural gas hydrate simulated reaction kettle in the axial direction, wherein the equal distances are 4 groups.
9. The device for evaluating the phase stability of the natural gas hydrate by the drilling fluid additive according to claim 8, wherein the reaction kettle temperature control system comprises a constant temperature box and a constant temperature box temperature control device, the constant temperature box is used for providing constant temperature required by experiments for the natural gas hydrate simulation reaction kettle, and the constant temperature box temperature control device is used for adjusting and accurately controlling the temperature of the constant temperature box in real time;
preferably, the temperature control range of the incubator is 0-100 ℃.
10. An experimental method of an evaluation device for evaluating the phase stability of a natural gas hydrate by a drilling fluid additive adopts the experimental device of claim 9, and comprises the following steps:
(1) and manufacturing the natural gas hydrate simulation reservoir
Pre-filling a sand sample into a natural gas hydrate simulation reaction kettle according to experimental design requirements, adjusting a second valve, a third valve, a fourth valve, a fifth valve, a sixth valve, a seventh valve, an eighth valve and a back pressure valve to be in a closed state after filling is finished, and opening a ninth valve and a first valve to remove air in an experimental pipeline by using a vacuum pump; closing the ninth valve, opening the fifth valve, the sixth valve and the seventh valve, and setting the total amount of injected natural gas according to the saturation of the natural gas hydrate; closing the fifth valve, the sixth valve and the seventh valve, opening the eighth valve, and setting the total amount of the injected clear water liquid according to the saturation of the natural gas hydrate;
(2) gas hydrate simulated reservoir permeability measurement
Adjusting the fifth valve, the sixth valve, the seventh valve, the eighth valve and the ninth valve to be in a closed state, opening the second valve, the third valve, the fourth valve and the back pressure valve, allowing nitrogen to flow into the natural gas hydrate simulated reservoir under the action of the gas booster pump, and measuring the permeability of the natural gas hydrate simulated reservoir after the parameters are stable; preferably, after the parameters have stabilized, the first gas reservoir pressure p is read1The pressure p of the first gas metering storage tank2Gas flow Q of the third gas flowmeter0And calculating the permeability of the natural gas hydrate simulated reservoir:
in the formula, kgPermeability, m, of a simulated reservoir of natural gas hydrate2；p1Inlet first gas storage tank pressure, Pa; p is a radical of2Metering the storage tank pressure, Pa, p, for the first gas at the outlet0Atmospheric pressure, Pa; mu is dynamic viscosity of nitrogen gas, Pa.s; q0Is the volume flow of gas at atmospheric pressure, m3And/s, A is the cross-sectional area of the simulated reservoir of the natural gas hydrate, and m2(ii) a L is the length of the natural gas hydrate simulated reservoir, m;
(3) evaluation experiment of drilling fluid additive on natural gas hydrate phase stability
Adjusting the first valve, the second valve, the third valve, the fourth valve, the fifth valve, the sixth valve, the seventh valve, the eighth valve, the ninth valve, the tenth valve and the back pressure valve to be in a closed state, adjusting the temperature and the pressure of an experimental system to be the temperature and the pressure set by the experiment, opening the eleventh valve, starting the second liquid high-pressure pump, the horizontal loading device and the drilling machine, adding conventional drilling fluid into a drilling fluid storage pool, performing a drilling circulation drilling experiment without drilling fluid additives, and performing dynamic distribution and hydrate decomposition rate of a natural gas hydrate decomposition interface in a simulated reservoir without drilling fluid additives;
preferably, a drilling circulation drilling experiment is carried out without the drilling fluid additive, the temperature and pressure changes at different positions in the natural gas hydrate simulated reservoir 41 are monitored in real time by the first temperature sensor 331, the second temperature sensor 332, the third temperature sensor 333 and the pressure sensor 333, and the temperatures T at different positions are measurediPressure piComparing the data with the natural gas hydrate phase state curve model, judging whether the natural gas hydrate at the position is decomposed or not, and measuring the decomposition rate v of the natural gas hydrate in real time by the fourth gas flowmeter 223iThe natural gas hydrate phase curve model is as follows:
in the above formula, T is the system temperature, K; Δ μ0Is the chemical potential difference between the empty hydrate crystal lattice and water in pure water in a standard state; t is0Is the temperature in the standard state, K; p is a radical of0Is the pressure at standard conditions, Pa; Δ H0Is the specific enthalpy difference between the empty hydrate crystal lattice and pure water, J/kg; Δ V is the specific volume difference between the empty hydrate lattice and pure water, m3/kg；ΔCpThe specific heat tolerance of the empty hydrate crystal lattice and pure water is J/(kg. K); r is a gas constant of 8.314J/(mol.K); n is a radical ofcThe number of components in the mixture which can generate hydrate; epsiloniThe number of i-type holes in unit water molecule in the hydrate phase; thetaijThe occupancy ratio of the guest molecule j in the i-shaped hole; f. ofwPa is the fugacity of water in the water-rich phase;
the fugacity of pure water under reference states T and p, Pa; if the type of hydrate, constant θijAnd CijCan be determined; meanwhile, the concentration of the drilling fluid additive can be obtained according to experimental measurement
A numerical value;
the dynamic distribution B of the natural gas hydrate decomposition interface in the simulated reservoir 41 of the natural gas hydrate drilled by the horizontal well without the drilling fluid additive can be derived in real time through the data processing system 35m,tAnd rate of hydrate decomposition vm,t；
And (3) repeating the step (1) and the step (2) by using an experimental device shown in the figure 1, starting a chemical agent metering pump and a tenth valve, pumping a drilling fluid additive with a set concentration into a drilling fluid storage pool, and continuously repeating the step (3) to measure and obtain the dynamic distribution of the natural gas hydrate decomposition interface and the hydrate decomposition rate in the simulated reservoir stratum of the natural gas hydrate drilled by the horizontal well containing the drilling fluid additive with the set concentration.
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